Epicanthal fold

An epicanthal fold, epicanthic fold, or epicanthus is a skin fold of the upper eyelid (from the nose to the inner side of the eyebrow) covering the inner corner (medial canthus) of the human eye. The presence of an epicanthal fold is present in people of East Asian and Southeast Asian descent, as well as other ethnic groups including some Native Americans and Africans. Epicanthal folds may also be seen in young children of any race before the bridge of the nose begins to elevate.

The term "epicanthal fold" refers to a visually categorized feature; however the underlying physiological reason and purpose for its presence in any given individual may be entirely different.

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In children

All humans initially develop epicanthal folds in the womb. Some children lose them by birth, but epicanthal folds may also be seen in young children of any ethnicity before the bridge of the nose begins to elevate. They may persist where birth is pre-term, and sometimes also where the mother is alcoholic.
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Epicanthal folds can cause a child's eyes to appear crossed, a scenario known as pseudostrabismus.

Pathological

In many caucasian backgrounds and other groups who don't commonly possess the trait, the presence of the epicanthal fold can be a symptom of fetal alcohol syndrome, chromosomal disorders such as Down syndrome (Trisomy 21),[2], Cri du Chat syndrome, or pre-term birth.

Inherited

There are numerous populations, across the world, that lack an epicanthic fold . However, the epicanthic fold is common in people of many, though not all groups of East Asian and Southeast Asian descent. It is found in significant numbers amongst Native Americans, the Khoisan of Southern Africa, many Central Asians and some people of Sami origin. It also present on people of Tibetan descent, especially Tibetans and North-East Burmese people. Due to classic genetics children of a parent with a pronounced epicanthal fold and one without an epicanthal fold will have varying degrees of epicanthal folds as a result.

In Asian ethnicities, the presence of an epicanthic fold is associated with a less prominent upper eyelid crease, commonly termed "single eyelids" as opposed to "double eyelids". The two features are distinct; a person may have both epicanthal fold and upper eyelid crease, one and not the other, or neither.

Surgical alteration

The procedure of reducing or removing epicanthal folds is epicanthoplasty. It is now an extremely rare procedure. Asian blepharoplasty, however, is a popular form of cosmetic surgery in East Asia.